Core and pole-piece for field-magnets of dynamos or motors.



N0. 68I,3|7. Patented Aug. 27, l90f. R. HIRSCI-l.

CURE AND POLE PIECE FOR FIELD MAGNETS 0F DYNAMOS 0R MOTORS.

(Application filed Ovt 19, 1899. Renew d June 29, 1901.! (No Modgl.)

2 Sheets-Sheet I.

g) Z w M I if M;

No. 68l,3l7. Patented Aug. 27, I901.

n. mnscn. con: AND POLE mac: run FIELDIAGNETS or uvumos on mamas.

j (Application filed Oct. 19, 1899. Renewed June 29, 1901.)

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io. ings, forming a part thereof.

UNITED STATE 5. PATENT OFFICE.

ROBERT nmscu, or MILwwKEE, WISCONSIN, ass'enon .OFONE-HALF 'ro WILLIAM 1;. \"O'IILOF SAM .rLAcE.

CORE AND POLE-PIECE FOR FIELD-MAGNETS OF DYNAMOS OR MOTOR-S.

SPECIFICATION forming part of Letters Patent him-681,317, dated August 27, 1901. Application filed October 19, 1899. Renewed June29, 1901. Serial No. 66,526. (No model.)

To all whom it nmyconccrn:

Beitknown thatLROBER'r HIRSOH,acitizen of the United States, residing at Milwaukee, in the county of Milwaukee and State of Wiscousin, have invented certain new and useful Improvements in Cores and Pole-Pieces for Field-Magnets of Dynamos or Motors, of which the following is a specification, reference being had to the accompanying draw- The main objects of my invention are. to increase the efliciency and to reduce the cost of dynamo-electric machines and motors.

It consists in certain novel features in the r 5 construction of the pole-pieces and cores of the field-magnets, as hereinafter particularly '4 described, and pointed outin the claims.

, In the accompanying drawings like letters designate the same parts in the several fig- 2o ures.

I Figure lis a side elevation of the cores and pole-pieces and of the supporting-frame of a four-pole electrical machine embodying my invention. Fig; 2 is a vertical cross-section of the same in a. plane parallel with the axis of the armature and indicated by the line 2 2, Fig. 1. Fig. 3 is a face view of one of the poleieces. Fig. 4 is a view corresponding with ig. 1, but on a smaller scale, showing a modified form of the cores and pole-pieces of the field-magnets. Fig. 5 is a vertical section thereof on the line 5 5, Fig. 4. Fig. 6 is aface view of one of the pole-pieces shown in Figs. 4 and 5. Fig. 7 is a diagram similar 5 to Figs. 1 and 4, showing for the purpose of comparison and explanation four polepieces the faces of which have the same areas, while the cross-sectional areas of the cores are different; and Fig. 8 is an end view of 4-0 still another form of pole-piece and core, the cross-sectional area of the core being the same as the area of the faces of the polepieces shown in Fig. 7, while the area of the face is smaller.

In the construction of dynamos and motors it is considered the best practice and is customary to construct the pole-pieces to extend around or cover circumferentially pole-pieces of a cross-sectional area not greater and oftentimes considerably less than two-thirds of the circumferential area of the armature, and sometimes the corners of the pole-pieces have been cut away in order to avoid leakage, thereby reducing the area of their faces below two-thirds of the circumferential area of the armature and to that extent reducing the magnetic ell'ect of the field upon the armature.

It iswell-known that the electromotive force of the current generated in the armature of a dynamo or motor depends primarily upon the number of ampere turns or windings in the field, the speed of tho armature, .and the length of armature-windings. I have found that by increasing the cross-sectional area' of the pole-pieces relatively to their faces the magnetic effect'of the field upon the armature will be materially increased with a given number of ampere turns or windings and that with pole-pieces and cores so'constructed a current of the required elec'tromotive force can. be induced by the field in the armature of an electrical machine, 7 5 particularly in machines of the smaller sizes, in which the increased efficiency is proportionately greater with a smaller number of ampere-turns, and consequently less weight of wire in the coils of the field,and with cores of smaller dimension radially than are re quired to induce such a current in machines as heretoforeconstructed.

Referring to Figs. 1, 2, and 3 of the drawings, AA designate the cores and pole-pieces, and B the frame,of -a four-pole electrical ma-- chine constructed in accordance with my invention. The faces a a of the pole-pieces are curved in conformity with the periphery of the armature, according to the usual and beto ter practice, and are made of an area equal to or greater than two-thirds of the circumferential area of the armature. From the faces a a the cores are beveled or rounded outwardly on the sides and ends, so as to increase 9 5 their cross-sectional area, and wire is wound around them in any of the usual ways to form field-magnets with shunt, series, or compound about two thirds of the armature. It has 50 also been the practice heretofore to make the windings. It will, be apparent that by this increase in the cross-sectional area of the loo cores and the consequent decrease in the number of ampere-turns required to produce a given electromotive force in 'the'armatnre the dimension of the cores radially with respect to the armature may be considerably decreased. By thus reducing the radial dimension of the cores the dimensions of the frame B transverse to the axis 'of the armature are correspondingly reduced and the-machine is made more compact as well as more eflicient. Since an increase in the cross-sectional area of the cores, as above explained,

the cores. The increased magnetic efficiency of the field being due rather to the disposition or arrangement of the iron than to an increase in its voluine,very'little, ii any, increase in the amount of iron over that employed in cores and pole-pieces of the ordinary construction will be required.

' Referringv to Figs. 4, 5, and 6, showing a modified construction, the cores AA are extended on the sidesonly and are of the same length parallel with the armature as the faces a a-. Whiie this construction does not increase the magnetic effect of the field to the same extent as that shown in Figs. 1, 2, and

' 3, :it nevertheless possesses great advantages and secures much better results than the or- 4 dinary forms of construction.

To illustrate the operative ettieiency under given conditions of a machine constructed in accordance with my invention and machines constructed-in accordance with the practice "which hasheretofore been followed, Iv have shown in Figs. 7 and 8-pole-pieces of the different forms A, A, A Afland A, the first twebeing like those shown in Figs. 1 and .4, respectively. The four pole-pieces shown in Fig.7 have faces of the same area, which, for

illustra ion, may be assumed'to be 46.155

square centimeters. The cross-sectional area of the core of the pole A is assumed to be '92g3 t'square centi meters; the area of the core of. pole A, 71.857 square centimeters; the

area of the core of pole A, 46.155 square cen- [34L39 square centimeters.

timeters, and the area of the core of pole A Assuming that machines are constructed with poles of the.

several forms shown in Fig. 7, the armatures of ail-be ng aiiire and turned at the rate of one thousand revolutions per minute and the field of each machine having eighteen hundred and ninety:ampere'tnrns, the electromotive force developed in them-mature of the machine having pole pieces like A, I have .foundto be 29.13 volts; that developed in the machine having pole-pieces like A, 21.04:

volts that developed in the machine having j pole-pieces like A 12.6 volts, and that de+ veloped in the machine havingpoie-pieces A machine constructed with pole-pieces like A, (shown in Fig. 8,) having faces of reduced area and cores of the same cross-sectional area as the core A, will under the conditions assumed with respecttd the forms shown in Fig. 7 develop an electromotive force in the armature of 12. 33 volts.

It will he. seenfrom the foregoing comparison that the efliciency of a machine provided with pole-pieces like those. shown in. Fig. 1

will be more than doubleth'at of a machine providedwith pole-pieces like that shown at A in Fig. 7, the most efficient form; of pole piece made, so far as I am swarm according to the present practice, and that the efiiciency of a machine provided with pole-pieces like those shown in Fig. twill be nearly double v that of a machine like A.

For the purpose of illustration and explaprovided with pole-pieces ie'd in a four-pole machine; but it is equally applicable to'machines having two era greater number of poles and to various types of machines, and I do not wish to be understood as limiting my invention to any particular constructiomexcept as to the construction. of the pole-piecesdefined in the following claims.

I claim-- Y 1. Cores and pole-pieces for the field-mag nets of dynamo-electric machines and motors, having faces of an area not less than twothi'rds of the circumferential area of the an mature, and a cross-sectional area greater than that of their faces, substantially-as and for the purposes set forth. 7 I,

2. Cores and pole-pieces for'the field-magnets of dynamo-electric machines and motors, having faces of an area no'tles'f's than twothirds of the circumferential area of the armature, and extended. on the sides beyond their faces so as to increase their cro s-sectional area, substantially as and for the pur poses set forth.

3. Cores and pole-pieces for the fieid-magnetsof dynamo-electric machines and motors, having faces of an area not less. than twothirds of the circumferen tial area of the armature and extended on the sides and ends beyond their faces so as oiiicrease their area in cross-section, substantially asand for the purposes set forth.

4. Cores and pole-pieces for the field-mag nation I have shown my invention as embod too nets of dynamo-electric machines and motors,

having curved faces of anarea not iess than two-thirds of the circumferential area of the armature, and extended on the sides so as to increase their area in cross-section. their sides being beveled next to their curved faces, substantially as and for the purposes set forth.

5. Cores and poie-piecesfor the field-mag nets of dynamo-electric machines and motors,

having curved faces of an area. not less than .In witness whereof 1 hereto aiiix mysi'gnntwo-thirds of the circumferential area of the ture in presence of two witnesses.

armature and extended on the sides and ends r 7 beyond 55m faces so as to increase their area RObERl HHQQ in cross-section, the sides and ends being bev- \\"itnesses: eied next to the eur'ved faces, substantially CHAS. L. Gross, as and for the purposes set forth. KENT l[. FLAXDEns. 

